Why is it so allegedlly dangerous to fit a 177 cal gas ram into a 22 cal air rifle thanks in advance?

I had to come back to this question several times before I realized what you were asking. You are talking about a Nitro ram in place of a Spring piston. I looked up the Nitro piston for air rifles and found that the web page stated that it must be installed by the manufacture, but they give no reason as to why they must do it. It's probably some sort of legality for the manufacture and they don't want to be sued if you are injured installing the conversion. I don't think the issue is going from a .177 to a .22, it's the installation itself that appears to be the problem.